Malus' law states that the intensity of plane-polarized light that passes through an analyzer varies as the square of the cosine of the angle between the plane of the polarizer and the transmission axes of the analyzer.

Forward Biasing is done by providing positive potential to p side of P-N Junction diode. This reduces the existing depletion layer and electron can easily travel through the depletion layer.

Desiging of a first order low-pass filter using op-amp (IC 741).

Zener diode is a heavily doped PN junction diode. Due to heavily doped, its depletion layer is very thin and is order of micrometer.